1. Field of the Invention
The present invention relates to an ophthalmic apparatus and, more particularly to an alignment mechanism provided in the ophthalmic apparatus, which aligns a measuring optical system set in a main unit so as to have a predetermined positional relation with an eye to be examined.
2. Description of Related Art
Ophthalmic apparatuses which perform examination, measurement and the like have an alignment mechanism to align a measuring system and others of the apparatus at a predetermined position with respect to an eye to be examined.
Alignment mechanism of conventional ophthalmic apparatuses is constructed of an alignment index forming optical system for projecting an alignment index onto a cornea of the eye to be examined, an observing optical system for observing the anterior part of the eye and an alignment reticle forming optical system for superimposing an image of reticle on an image of the anterior part under observation through the observing optical system.
For carrying out alignment of the apparatus provided with the alignment mechanism, operators (examiners) have moved the main unit with a joystick and the like with respect to a base table so that the above-mentioned optical systems of the apparatus may be positioned in a predetermined relationship with the eye to be examined. Thus, alignment of the apparatus has been carried out.
The alignment mechanism mentioned above has the advantages of relatively simple construction and easy operation.
However, when using ophthalmic apparatuses needing particularly precise alignment, such as a non-contact type tonometer, operators must perform fine alignment operation. In the case of an inexperienced operator at operating the apparatus, accordingly, there exist problems in that he takes time to operate the apparatus and precise alignment is difficult for him.